Pitch Black Skies

16 minutes ago, newbie alert said:

Sorry I don't follow, I haven't got a heq5 but I don't understand what you're trying to mesh and then you say Ra is always meshed?

He's just saying to loosen the mesh between the worm gear and the RA gear ⬇️

and then mesh them back together gradually with the grub screws.

When he said RA is always meshed he was referring to getting the best results rather than having a fraction of play between the mesh.

9 minutes ago, Jamgood said:

(I hadn't got the dew shield on for the photo but I do use one.)

Very nice set up 👌🏻

I leave mine on all the time as I do my flats with it in place.

I see you have one on the guidescope. Can they be bought?

@alacant Cheers, all done. Will report back when I get a clear spell.

Guys, this gear that I'm turning. I can get it either rotating very easily with a slight fraction of play, or rotating a bit stiffly with zero play. I'm not sure which is correct.

Folks,

Lets see your 130P-DS in action and how you've modified it.

Always interested to see how others use and modify theirs.

11 hours ago, alacant said:

Ah, ok. That's the cone bearing at the base of each axis which simply needs loosening

Yep, that has made a huge difference. Looks like I didn't need to buy the set of bearings after all.

@newbie alert Cheers, the worm was just pressed a little too tight against the drive. I fixed it in the last post with the 2 grub screws.

The other night I was checking for backlash and I adjusted until there was binding and then backed off just enough until the binding stopped. I suppose it just goes to show, you can't really do it by ear. For the best results,  it's better to strip down I think. I'll just have to wait about a week or two now for a clear night to test it all 😌.

Gonna take a look at the axis's locking nuts too, it's possible they can be loosened slightly to help with balance.

Edit, locking nuts were too tight. There is a huge improvement now in both axis's. It's much easier to find a perfect balance.

The worm drive seems to be way too tight on both axis's. The gear is really stiff. I'm surprised I'm not getting binding. I've adjusted it now. It's moving freely with zero play. I've put the belt back on and it seems more responsive when a little tighter.

The DEC backlash seemed considerable, however the guiding numbers in DEC were great. This is when the belt had a bit of slack. I've tightened it since but haven't tested it.

The spike seems to only be in the RA axis though.

@vlaiv @newbie alert

I think it might have something to do with my belt tension. I have it super tight. I wonder if it is causing the pulley to oscillate? I'll test it tomorrow.

When I don't have the belt super tight, I can manually twist one of the gears slightly without the opposite gear turning. It's the equivalent of backlash I presume.

@vlaiv I'll have to do a bit more investigating. That's a really useful page you've found there.

This one is from March 25th. It's M51 in East location. No houses.

This looks more sporadic.

Maybe this will shed some more light on it?

It's not as consistent in this snapshot but there's clearly a spike in the RA 60-90secs or so.

@newbie alert It's a HEQ5, Rowan modding hasn't helped.

I reckon it's something that is rotating as it's quite consistent.

@alacant Cheers, I'll definitely lower the aggressiveness to stop overshooting.

I have a complete set of bearings ordered and some grease so hope this will help improve it.

Both axis's were very stiff on this mount from brand new. It's not easy to find perfect balance when it's like this.

I've noticed a consistent spike in my RA tracking.

It happens about every minute.

What mechanical part of the mount is this most likely to relate to? What component if any does a complete rotation at tracking rate in 1 minute?

I'm guessing the worm drive or maybe one of its bearing but I would like to know what you think.

28 minutes ago, Olli said:

Thanks everyone for all the help. Still feel a bit overwhelmed by it all lots to take in. Will probably have to write a list what I’ll need In the future.. but for now though to get started with imaging what targets do you recommend I should try and shoot for the first time this season?  For using a dslr I’ve seen that darks and lights are used. Is this a necessary process? Do you then stack it all with the others?

You'll see this mentioned a lot throughout threads and it still rings true, and that's to read 'Every Photon Counts' before deciding to buy anything. It will give you an understanding of what equipment you need, some seasonal targets to image, and how to image in general. It's very useful for when you're just starting out as it will answer a lot of your questions.

https://www.firstlightoptics.com/books/making-every-photon-count-steve-richards.html

24 minutes ago, Olli said:

Can I ask what PEC training is ? AAP sounds like a firm favourite will definitely see if I can get one. 

Well worth it. I started with my laptop, an EQDIR cable and NINA. It's excellent but I found the AAP much more user friendly and very neat and tidy in regards to wiring.

Your going to need an EQDIR cable either way, so maybe get that first and you can explore NINA or some other software before deciding on getting an AAP.

PEC training is periodic error correction training. Check out this great video from Astrobloke. He explains it very well.

7 hours ago, vlaiv said:

nor is polar alignment only source of the error

Do you think cone error can have much of an impact on star trailing?

I corrected mine last night, it was way off. 

I had the mount pointing at Polaris, then with the RA level I centered Polaris in the reticle. As I moved the RA in opposite direction Polaris moved rapidly out of the field of view. With minor adjustments to my dovetail screws I was gradually able to get the star to stay centered through a whole 180° turn of the RA. It was a tedious job.

It makes me though, if targets are behaving like that when the RA is turning, is it possible this is putting my guiding under pressure?

Sorry to hijack the thread, but I think this might be useful to anyone reading.

+1 for AAP

It's worth it's weight in gold. Makes life so simple when starting out.

My only grievance is that it doesn't allow PEC training, so your guiding is forever compromised.

Aha that makes sense, I forgot to convert to 14-bit values.

@vlaiv to the rescue again 💪

You're going to have to start charging at this rate

24 minutes ago, vlaiv said:

I made above measurement on ASI1600 - got 62 from dark with 64 offset, so I think multiplier is 1 for that camera (if there is indeed integer multiplier for each camera).

Great stuff, yes it seems this camera is by 1, making things easy.

Can't understand why mine is being multiplied by 10 and Fegato's by 8???

I don't think a lot of people know about this. The mentioned equation on CN wouldn't ever have worked for them.

My camera is reported to have 1.5e- of read noise at unity gain 100

Using this calculator, I get a figure of 6.37e- read noise.

Is this correct?

25 minutes ago, Fegato said:

Quite why they would use 10 for the ASI533 and 8 for the ASI2400, I really don't know

Yes it seems to be different for different models, 'ZWO has this thing for obscure offset settings that seem to be different in every camera. The offset you select in the driver needs to be multiplied by some number to get your value in ADU. I believe in the 183 the offset multiplier is 5 and the 294 it is 16 (please correct me if Ím wrong)' (ERHAD).

What would it be for an ASI1600?

If someone has a bias frame from a ASI1600, we could measure it to find out.

What's still confusing me is that Jon uses 50 as the offset figure in his formula on the CN thread you linked. This gave me the impression he was using the default offset setting within the driver which is why I was using 70 in my equation, but using that figure is incorrect. It needs to be converted to ADU. Is it possible he is using the default offset setting or has he already converted it to ADU? It seems unlikely.

Anyone got a asi1600 bias sub handy???

First attempt at a globular cluster, 1hr 40mn

Hercules Globular Cluster (M13)

I've found the answer.

With this camera the offset number gets multiplied by 10 to get the value in ADU's.

70*10 = 700

As you've shown me Vlaiv, this figure is 14-bit so to get 16-bit figure we multiply by 4 .

2^(16-14) 

= 2^(2)

= 4

700*4= 2800

My bias frame measured as 2796. Quite close.

Things are finally starting to make sense 😬